The present invention relates generally to electronic logic circuits, and more specifically to a master-slave flip-flop.
Master-slave flip-flops are commonly used in the design of integrated circuits. They are reliable, stable and their state changes are predictable. However, a penalty in terms of surface area on an integrated circuit chip must be paid because each data bit to be stored in a flip-flop requires two parts, a master and a slave. When many bits are to be stored, such as in a register file memory for a microcomputer system, a fairly large space penalty is paid when master-slave flip-flops are used.
It would be desirable to provide circuitry for storing multiple logic bits without paying the surface area penalty extracted by multiple master-slave flip-flops.
Therefore, it is an object of the present invention to provide circuitry suitable for use in a computer system which provides the benefits of master-slave flip-flop storage without the usual space penalty.
Therefore, in accordance with an aspect of the present invention, a single flipflop master cell drives multiple flip-flop slave cells. The slave cells are separately addressable. A savings in chip surface area is thus realized. The multi-slave flip-flop can be integrated onto a CPU or other computer system chip.
In accordance with another preferred embodiment, twenty-two slave flip-flop cells are grouped together into two groups of eleven. Each group of eleven has a single master cell controlling that group. These twenty-two cells define one bit of a data storage structure, preferably two individually addressable register files. A desired number of these storage structures are grouped together to define a register file that is a desired number of bits wide. In accordance with another feature of the other embodiment, the two groups of flip-flops are accessible by two separate data paths of a processor operating in parallel.
The novel features which characterize the present invention are defined by the appended claims. The foregoing and other objects and advantages of the present invention will hereafter appear, and for purposes of illustration, but not of limitation, two preferred embodiments are shown in the accompanying drawings.